Here’s a desmos graph I made a while ago which shows how my team did odometry last year:
Keep in mind that odometry uses basic trigonometry, so if you still don’t understand it you should try learning that first.
This version of odometry assumes the robot moves in straight lines, but it works good enough if you run it fast enough (we ran it every 10 milliseconds). The pilons document explains doing odometry using arcs which I think is more accurate, but my team hasn’t been able to compare them a lot yet.